1. Field of the Invention
The present invention relates to a wind turbine generator having a detection unit for detecting a foreign object inside a rotor and an operating method of the wind turbine generator.
2. Description of the Related Art
In a wind turbine generator, for example, the wind turbine generator being equipped with blades and a rotor hub is rotated, and the rotation of the rotor is transmitted to a generator via a rotation shaft so as to rotate a shaft of the generator, thereby generating electricity. The rotor hub for example houses a variety of devices such as a pitch control mechanism for adjusting the pitch angle of the blades in accordance with the wind conditions (e.g. wind power and wind direction). These devices are fixed for example directly to an inner wall of the rotor hub or via a mount to be installed in the rotor hub by bolts.
During the operation of the wind turbine generator, the bolts that fix the devices such as the pitch control mechanism inside the rotor hub may become loose by the rotation of the rotor hub, and the bolts and components consisting the devices may fall off. Occasionally, workers conduct inspections inside the rotor hub and may leave tools inside the rotor hub. When foreign objects such as materials that fell off and the tools exist in the rotor hub, the devices inside the rotor hub can be significantly damaged with the rotation during the operation of the wind turbine generator.
Patent Document 1 discloses to use a sound pick-up to detect the abnormality of the blades, the generator and a drive-train by using an acoustic monitoring system, although this does not take measure to detect the foreign objects inside the rotor hub.